1. Field of the Art
This invention relates to a manual control knob for an endoscope, and more particularly to a manual control knob to be mounted on a manipulating head assembly of an endoscope for angularly bending a fore end portion of an insertion instrument, and a method for manufacturing such endoscopic manual control knob.
2. Prior Art
Endoscopes have been and are widely used in medical purposes. In most cases endoscopes are constructed as shown schematically in FIG. 5, including a manipulating head assembly 1 to be gripped by an operator, an insertion instrument 2 which is extended out on the front side of the manipulating head assembly 1, and a universal cable 3 which is led out on the rear side of the manipulating head assembly 1. Provided at the fore distal end of an elongated flexible body portion 2c of the insertion instrument 2 is a rigid tip end section 2a with an illumination window or windows along with an endoscopic observation window for endoscopic observation purposes. Further, provided between the rigid tip end section 2a and the flexible body portion 2c is an angle section 2b which can be angularly bent by remote control to turn the rigid tip end section 2a into an arbitrary direction. On the other hand, the universal cable 3 is provided to connect the manipulating head assembly 1 at least with a light source.
As well known in the art, the angle section 2b of the endoscopic insertion instrument 2 has a flexible articulate structure which can be bent at least in one direction by remote control. Normally, the angle section 2b is arranged to be bendable in four directions, i.e., in upward, downward, rightward and leftward directions. The angle section 2b is bent in one of these directions by way of an angle manipulation mechanism which is provided on the manipulating head assembly 1 of the endoscope.
Shown in FIG. 6 is an angle manipulation mechanism. As clear therefrom, a support plate 5 is provided internally of the manipulating head assembly 1 to mount thereon a tubular support column 6, which rotatably supports a pair of upper and lower pulleys 7 and 8. Upon rotating one of the two pulleys 7 and 8, say, the pulley 7 about the support column 6, the angle section 2b of the insertion instrument is bent laterally in a rightward or leftward direction. Upon turning the other one of the pulleys 7 and 8, say, the pulley 8 about the support column 6, the angle section is bent vertically in an upward or downward direction. In order to bend the angle section 2b in this manner by remote control, a pair of upper and lower operating wires 9 are connected to the pulley 7, while another pair of right and left operating wires 10 are connected to the other pulley 8.
The pulleys 7 and 8 are connected to hollow inner and outer rotatable shafts 11 and 12, respectively. The pulley 7 which is located on the side of the support plate 5 is connected to the inner rotatable shaft 11. The pulley 8 which is located on the upper side of the pulley 7 is connected to the outer rotatable shaft 12. These rotatable shafts 11 and 12 are provided coaxially with the support column 6, and are led out to the outside of a casing of the manipulating head assembly 1 of the endoscope. Manual control knobs 13 and 14 are connected to outer ends of the rotatable shafts 11 and 12, respectively.
When the insertion instrument 2 is introduced into a body cavity, while gripping the manipulating head assembly 1 at the upper end of the insertion instrument, an operator can manipulate the manual control knobs 13 and 14 of the angle manipulation mechanism 8 to bend the angle section of the insertion instrument in a desired direction. The angle manipulation mechanism 4 is provided with lock means 15 and 16 thereby to lock the knob members 13 and 14 against rotational movements for retaining the angle section 2b in a bent state whenever necessary.
The manual control knob 14 which is adopted for bending the angle section 2b in upward and downward directions is shown more particularly in FIGS. 7 and 8. In these figures, indicated at 20 is a molded knob body proper of the manual control knob 14. Through a link member 21, the knob body 20 is securely fixed to the rotatable shaft 12 by means of a screw 22. The knob body 20 is provided with an aperture 23 in its top plate portion 20a to receive the rotatable shaft 12, and the above-mentioned link member 21 is connected to the top plate portion 20a. A peripheral side wall portion 20b is contiguously provided around outer periphery of the top plate portion 20a. These top plate portion 20a and the peripheral side wall portion 20b are formed integrally by synthetic resin molding. The molded knob body 20 is provided with a plural number of lever portions 24, which are projected radially outward from a plural number of positions (five angularly spaced positions in the particular example shown) around the outer periphery of the knob body 20. For turning the knob body 20, an operator puts his or her fingers on the lever portions 24 and push the lever portions 24 to turn the knob body 20 in a desired direction. For this purpose, finger grip surfaces 24a are provided on outer distal end faces of the lever portions 24. In the following description, the molded knob body 20 is assumed to have the top plate portion 20a on the top side, and the outwardly projected lever portions are regarded as outer peripheral portions of the knob body.
In order to turn the manual control knob 14 (or the other manual control knob 13), while gripping the manipulating head assembly 1 of the endoscope in one hand, an operator can put his or her thumb on one of the finger rest surfaces 24a in outer peripheral portions of the knob body 20 to apply a force in a direction the knob member 14 is to be turned. Accordingly, in order to permit an operator to apply a sufficient operating force easily on the knob member 14, it is desirable for the knob body to have a broad finger grip surface on the lever portions. Namely, the finger grip surface 24a on the lever portion 24 should have not only a sufficient breadth in the circumferential direction but also a sufficient height (in a direction substantially parallel with the longitudinal axis of the rotatable shaft 12).
The top plate portion 20a and the peripheral side wall portion 20b of the knob body 20 are formed integrally together by synthetic resin molding, providing lever portions 24 with finger grip surfaces 24a of a large breadth both in circumferential and axial directions. In case the knob body 20 is molded to have solid lever portions 24, there may arise a problem of shrinkage surface sinking, which often results in sunken spots on the surfaces of molded lever portions 24. Such surface sinking can impair the maneuverability and appearance of the knob members to a considerable degree especially in case sunken spots exist on the surfaces of the lever portions 24. The problem of shrinkage surface sinking has thus far been prevented by reducing the thickness of the top plate portion 20a and side wall portion 20b of the knob body 20 to a minimum necessary thickness which would be allowable in terms of strength, as shown in FIG. 8.
The lever portions of the knob members, especially the finger grip surfaces of the lever portions which are repeatedly touched by the fingers of an operator get contaminated easily. Normally, each time an endoscope is washed clean after use. More particularly, an endoscope is washed by immersing the entire body of the endoscope in a cleaning liquid, including not only the insertion instrument, which has been directly introduced into a body cavity, but also the manipulating head assembly and the universal cable of the endoscope. At this time, the manual control knobs of the angle manipulation mechanism are also washed in the cleaning liquid. However, it is often found difficult to clean back side of the respective lever portions and corner portions between the top plate portion and the side wall portion of the knob member to a satisfactory degree.
In an attempt to overcome the above-mentioned problem or difficulty, it has been known, for example, from Japanese Laid-Open Patent Application H11-47082 to fill cavity on the back side of each lever portion with a back nail member in the form of a block of the same synthetic resin material as the knob body and welded to the latter. Namely, in this case, while reducing the wall thickness of the knob body to a minimum necessary thickness which is free of shrinkage surface sinking in a molding stage, the hollow cavity on the back side of each lever portion of the molded knob body is completely filled and closed with the back nail member.
However, in the case of the prior art knob construction just mentioned, the fabrication process becomes complicated and involves an increased number of steps because of the necessity for a step of molding the back nail members in addition to the molding of knob bodies and a step of welding molded back nail members to the back side of the respective lever portions of the knob body. This naturally results in increases in production cost. Besides, unless the back nail members are thoroughly welded to a knob body, there are possibilities of contaminants still remaining in interstices or clevises at incompletely welding portions even after a careful cleaning or washing operation.